In the flat type solid oxide fuel (SOFC) disclosed in the patent document 1, each single cell is composed of a porous fuel electrode, a electrolyte film formed on the surface or the rear face of the porous fuel cell, an air electrode (cathode) film formed on the electrolyte film, an interconnector film formed on the other face of the porous fuel electrode, and a porous air electrode contacted with the air electrode film. Then, the single cells are stacked up and manifold boards are attached on the respective sides of the obtained stack in order to form a cell stack. As the fuel electrode, a sintered body of a mixture of nickel (nickel oxide in the manufacturing process) and yttria stabilized zirconia (YSZ) is disclosed.
As for the interconnector (it is also called “separator”), it is demanded to be dense so as to separate the supplied fuel gas and air without mixing them, to have a high electrical conductivity in order to connect electrically the adjacent cells mutually, and to have an thermal expansion coefficient which is analogous to those of other components of the cell. Lanthanum chromite-based oxides have been used as the material for the interconnector which can satisfy such demands. Moreover, it has been also done to dope calcium to the lanthanum chromite-based oxide in order to obtain a dense film. As methods for forming the interconnector film, slurry coating method, coating and thermal decomposition method, and sol-gel method are disclosed in the patent document 1.
Patent document 1: PCT/JP99/02897 (International publication No.: WO 00/74159)